Since 2004, a series of robotic security guards have been roaming the perimeter of the Hawthorne Army Depot in Nevada — part of a pilot program, to see if unmanned systems can help maintain security at military installations. After 8,000 hours on patrol, the Army has been impressed, apparently. The service is ordering up to 24 more of the “Mobile Detection and Assessment and Response System,” or MDARS, at a cost of $40 million.The diesel-powered robots, in development since 1989, operate “at speeds up to 20 miles per hour and can run for 16 hours without refueling,” according to its manufacturer, General Dyanmics. “Using radio frequency identification tags, MDARS keeps track of inventory, as well as gates, locks and other barriers.”

Next-gen models could include “improved response speed of at least 30 mph… intruder detection while MDARS is moving, and intruder detection out to 1500 meters,” as opposed to 300 meters, today.

The machines could also be armed. MDARS has been tested with automatic rifles and non-lethal weapons. And General Dynamics is boasting that they new versions will have “non-lethal weapons with an engagement range of at least 30 meters.”